1. Field of the Invention
The present invention relates to a structure of a bonding apparatus.
2. Related Art
In semiconductor manufacturing processes, wire-bonding apparatuses are often used for bonding of thin metallic wires to electrode pads on a semiconductor chip and electrode leads on a lead frame for connection therebetween. Many wire-bonding apparatuses include a bonding arm configured to be rotated by a drive motor, an ultrasonic horn attached to the bonding arm, a capillary attached at one end of the ultrasonic horn, and an ultrasonic vibrator attached to the ultrasonic horn. In such wire-bonding apparatuses, the bonding arm is driven and rotated to move the capillary in a direction toward and away from a pad or lead and to bond an initial ball formed at a tip end of the capillary or a wire to the pad or lead, and then the ultrasonic horn is resonated with the ultrasonic vibrator to provide ultrasonic vibration at the tip end of the capillary for performing a bonding operation.
Such wire-bonding apparatuses also include a control unit for controlling the application of a current value to the drive motor and ultrasonic vibrator to provide a predetermined bonding load and ultrasonic output during bonding.
For successful bonding with such a wire-bonding apparatus, it is necessary to detect and feedback a bonding load, ultrasonic output, and the like provided from the capillary to pads and leads during bonding.
For this reason, Japanese Unexamined Patent Application Publication No. 10-256320 proposes attaching a strain gauge to an ultrasonic horn and, using this strain gauge, detecting a bonding load and ultrasonic vibration to control the application of a voltage to a drive motor and an ultrasonic vibrator.
Japanese Patent No. 3530139 also proposes providing a load detecting sensor and an ultrasonic vibration detecting sensor made of piezoelectric material on the same plane between a capillary and an ultrasonic vibrator, and detecting bonding load and ultrasonic vibration outputs from the respective sensors.
In contrast, the state of ultrasonic vibration at the tip end of the capillary varies at different times from the start of bonding, during bonding of an initial ball, to the end of the bonding of the initial ball, and the same applies to vibration loads at the tip end of the capillary. In this respect, the related arts described in Japanese Unexamined Patent Application Publication No. 10-256320 and Japanese Patent No. 3530139 can detect the change in the ultrasonic output of the ultrasonic horn itself, but not the change in the vibration at the tip end of the capillary, which is much smaller than that of the entire ultrasonic horn.
Also, in the related arts described in both Japanese Unexamined Patent Application Publication No. 10-256320 and Japanese Patent No. 3530139, the load sensor is attached at a site of the ultrasonic horn at which the amplitude of ultrasonic vibration emerges, suffering from a problem in that the sensor attached to the ultrasonic horn affects the ultrasonic vibration and thereby has some impact on the bonding performance. Further, changing the ultrasonic horn as appropriate also requires the sensor to be changed, suffering from a problem of taking a long time for maintenance because it is necessary to make an adjustment such as a calibration at every change of the ultrasonic horn.